Stade Francais are refusing to back down in their dispute with England over James Haskell.
The French side have demanded that former Wasps flanker Haskell returns to Paris ahead of their Top 14 clash with Toulouse.
However England have claimed they are not obliged to release the 24-year-old from their RBS Six Nations training camp having negotiated a deal with Stade over his availability at the start of the season.
Stade, though, have hit back by insisting no agreement is in place and that Haskell must return to training this week.
A statement on the club's official site read: "On Monday, Stade Francais - finding England international James Haskell absent from training - asked the back-rower to return immediately to Paris.
"This period is not provided for in the IRB's international windows and Stade Francais have a big match against Stade Toulousain on Saturday.
"The RFU responded that they will refuse to release Haskell on the grounds that an agreement was signed between them and Stade Francais. No agreement has ever been signed with the RFU, contrary to what they claim. If it is so, the RFU can produce this so-called agreement.
"The RFU have surely confused us with other clubs such as Toulon, who had to accept an agreement for this season relating to Jonny Wilkinson.
"Therefore, Stade Francais are ordering James Haskell, who has already missed two training sessions, to kindly rejoin his club urgently.
"The RFU have signed agreements with English clubs, whom they reimburse for placing their international players at their disposition outside of IRB international windows. This is not the case for French clubs who, thus, do not have to fund the preparation of the England team."